Give makes the Monokey and Monolock systems. The Monokey is more durable, but much more expensive, and you'll have to buy a mounting plate. The Monolock comes with the plate. All are available in various sizes. I have a Monokey on my Guzzi and a Monolock on one of our scooters. I'm not really sure it's worth spending 2-3x more on the Monokey.
Hepco Beckers are nice, but harder to find, I think.
Shad makes good quality cases as well, and they also come with mounting plates.